The transformation of waste cellulosic materials into useful products has been studied for many years. Immense volumes of waste cellulosic products, such as wood, sawdust, hay, cornstalks, bagasse, pulp, paper, etc. are produced each year and, for the most part, are burned because there is no alternative economical use for the waste materials. It is known, however, that these cellulosic materials can be hydrolyzed into mono-sugars, such as glucose and xylose, which have utilities in the production of alcohol by fermentation and as a feed for ruminants, respectively. While processes to produce alcohol from waste cellulosic materials have been commercialized in the past,those processes have generally been abandoned in favor of more efficient processes which catalytically treat natural gas or petroleum products to produce methanol and ethanol. The economics of natural gas and petroleum have, of course, in more recent years suffered because of the rising costs for these basic materials, and accordingly, the processes for producing alcohol from cellulose are now much more favorable than anytime during past decades.
It has been known that cellulosic fibers, regardless of their source, always include alpha-cellulose, hemicellulose, and lignin, the proportions of these three components varying with the type of biomass. The two types of cellulose are capable of being hydrolyzed by acid treatment to mono-sugars, while lignin is not capable of being converted to such materials. In order for the acid treatment to function efficiently the natural form of crystalline alpha-cellulose must be decrystallized into an amorphous form. Subsequently, the amorphous alpha-cellulose can be hydrolyzed to glucose while hemicellulose can be hydrolyzed to xylose. The decrystallization of alpha-cellulose is known to be accomplished by dissolving it in a concentrated strong mineral acid. Hydrolysis of amorphous cellulose is known to be accomplished by treating the material under heat in the presence of an aqueous, mineral acid catalyst. While these processes have been known generally for many years, they have not been refined to produce efficiently and economically a solution fermentable by yeast and a syrup for feed to ruminants.
It is an object of this invention to provide an improved process for the decrystallization of alpha-cellulose. It is also an object of this invention to provide an improved process for hydrolyzing decrystallized alpha-cellulose and hemicellulose to recover an aqueous solution of glucose and xylose, respectively, and the residual lignin. Other objects will appear from the more detailed description of this invention which follows.